The male koala has a large two-pronged penis, and the female koala has three vaginas and two uteruses. (see photos below).
Koalas, like all marsupials, have a single opening at the bottom of their body, called a cloaca. The animal's intestinal, urinary, and genital tracts are connected to this single-opening cloaca. As a result it poops, pees and has sex through the same opening, much like birds and reptiles.
Placental mammals such as dogs, cats and humans have two or three openings. One for each of the following; the anus, the urinary tract and the reproductive tract.
Male koalas have a long two-pronged penis (bifurcated penis). The end of the penis is split into two prongs (see photo). This means that each prong enters the female's corresponding left and right vaginas.
Also, the male koala's penis is located behind its scrotum. (Most animals have the penis located in front). When flaccid, the koala's penis is withdrawn and safely tucked away inside its cloaca.
Koalas have a fur-covered non-pendulous scrotum. This means their scrotum (balls) are held close to their bodies. They do not dangle.
Male koalas do not have a pouch. Males begin mating at about three years of age.
The female koala has three vaginas and two uteruses (uteri). The two outermost vaginas are used for sperm transportation to the two uteruses above them. Babies are born through the middle vagina. By contrast, female placental mammals have only one uterus and one vagina. (See photo).
The female koala gives birth to a tiny, underdeveloped baby. Females can breed from about two years of age.
Koalas give birth to a tiny embryonic baby that crawls from its mother's birth canal to a pouch located on the front of the mother’s body.
It carries this little baby in a pouch equipped with nipples. The baby attaches itself to a milk nipple and continues to grow into a viable baby koala.
The koala's pouch has an upward-facing opening that can be drawn shut by powerful muscles to prevent the baby from falling out. This pouch is also lined with muscles and ligaments that expand to accommodate the growing joey inside.
Only female koalas have a pouch. The female koala isn't born with a pouch. Her pouch develops as she begins to reach sexual maturity.
No. Koalas don't have belly-buttons. Only placental mammals like you and me, cats, cows, whales, etc., have belly buttons. That’s because placental mammal babies have an umbilical cord which originally connected where the belly-button is.
The inside of the pouch is warm, nearly fur-less, with two teats that supply milk. Because koala babies are born underdeveloped, her pouch acts as a second womb, allowing her young to grow into viable offspring.
Koalas have sex between September and March and have one offspring per year.
During mating season, male koalas make loud bellowing mating calls. These calls are unique to each male and advertise its size and fitness to female koalas nearby. Scientists were surprised to discover that it is not the largest, most dominant male that gets to mate with a female. Instead, the female uses the male's mating call to identify her previous suitors. She seems to prefer a new partner each mating season.
The male koala's sperm contains special chemicals that trigger the female's ovulation.
A unique feature of these animals is that during extreme drought and starvation, the female koala can practice birth control by putting the babies growing in her uteruses "on hold", stopping their future development until conditions improve. This is called embryonic diapause. Then, when the mother's pouch becomes free, the next baby will be born, and the fertilised egg will start developing into a new foetus.
The koala egg descends from an ovary into a uterus, where it is fertilised. Once fertilised, the egg is encased in a fragile shell just a few microns thick. This shell disintegrates when the egg reaches the third gestation phase.
Koalas only develop a very 'primitive' choriovitelline placenta where the egg, with its embryo inside, is attached to the mother's uterine wall for 30 to 36 days.
A koala female is pregnant for 30 to 36 days. Before the birth of a young koala, the female cleans out her pouch by sticking her head into it and licking it clean. It then takes up a "birthing position" and licks its birth canal opening to stimulate the birth.
The young koala, about the size of a jelly-bean, soon emerges from the birth canal. It is born blind, deaf, hairless, with stumpy forelimbs and hardly any trace of its hind legs. Even though it is still underdeveloped, the young newborn has an excellent sense of direction and an acute sense of smell, knowing which way is up and down. Using its little forelimbs in a swimming motion, the young joey crawls laboriously to its mother's fur to the pouch. This journey takes about three minutes. The joey's journey is made entirely by itself. The mother does not assist in any way. Once inside its mother's pouch, the joey quickly attaches itself to a nipple in the pouch.
Once it has attached itself to its mother's nipple, the young joey will stay hidden for about six months. Then it will start to tentatively pop its head out of its mother's pouch and observe the world around it. Finally, after having gained enough confidence, it will venture out of the pouch. The young joey will hitch a ride on its mother's back for 6-12 months before it becomes fully independent.